1. Field of the Invention:
The present invention relates to a process for the sulfation of alkyloligoglycosides.
2. Discussion of the Background:
Sulfated alkyloligoglycosides are useful as foaming agents and dispersants in rinsing agents, detergents, and cleansers. They are anionic surfactants which are used in the formulation of cosmetics and are used in tertiary petroleum recovery.
U.S. Pat. No. 1,951,784 describes sulfuric acid esters of alkyloligoglycosides which are prepared by the simultaneous reaction of saccharides or starch with sulfuric acid and an alcohol. In this process, sulfuric acid esters of the alcohols used are also formed to a substantial extent, which clearly reduces the yield of the desired product. However, if the starting materials are alkyloligoglycosides that have a melting point in the range of 150.degree. C., sulfation temperatures above 100.degree. C. are necessary. At these temperatures, acetal cleavage occurs, whereupon the liberated alcohols are likewise converted to sulfuric acid esters. Glucose is also liberated, which is charred to carbon under these conditions.
EP-A-280 715 describes a process in which alkylglycosides are sulfated using a sulfur trioxidetrimethylamine complex in dimethylformamide under mild conditions in 19 to 24 hours. This process is costly because of the use of the special reagent. The high boiling point is also a drawback in the recovery of solvent by distillation. A need therefore continues to exist for a method of sulfating alkyloligoglycosides under mild conditions.